Cable-driven system with magnetorheological fluid clutch apparatuses

ABSTRACT

A tensioning set comprises an output member. A magnetorheological fluid clutch apparatus is configured to receive a degree of actuation (DOA) and connected to the output member, the magnetorheological fluid clutch apparatus being actuatable to selectively transmit the received DOA through the output member by controlled slippage. A tensioning member is connected to the output member so as to be pulled by the output member upon actuation of the magnetorheological fluid clutch apparatus, a free end of the tensioning member adapted to exert a pulling action transmitted to an output when being pulled by the output member. The tensioning set, or a comparable compressing set, may be used in systems and robotic arms. A method for controlling movements of an output driven by the tensioning set or compressing set is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 15/551,197 filed on Aug. 15, 2017, which is a 371 ofInternational Application No. PCT/CA2016/050191 filed on Feb. 25, 2016,and claiming priority of U.S. Patent Application No. 62/120,556, filedon Feb. 25, 2015.

FIELD OF THE APPLICATION

The present application relates generally to magnetorheological (MR)fluid clutch apparatuses, and more particularly, to cable-driven systemsusing such apparatuses.

BACKGROUND OF THE ART

State-of-the-art distributed power devices rely on hydraulics orelectromagnetic actuation. Hydraulic actuation is reliable towardsmechanical jam, but has fundamentally limited dynamic response andefficiency. Furthermore, implementation of hydraulic systems intocommercial applications may be problematic as hydraulics are prone toleakage, leading to increased maintenance costs. Moreover, hydraulicactuation is hardware intensive.

Electromagnetic actuation offers a clean alternative to hydraulicactuation. For high dynamic applications, the most common form ofelectromechanical actuation is found in direct-drive motors, which areprohibitively heavy. Device weight can be considerably reduced byproviding a reduction ratio between the motor and the end-effector.Indeed, when coupled to reduction gearboxes, electromechanical actuatorsare lighter and less expensive than direct drive solutions, but theirhigh output inertia, friction and backlash may diminish their dynamicperformance.

Magnetorheological (MR) fluid clutch apparatuses are known as usefulapparatuses for transmitting motion from a drive shaft with precisionand accuracy, among other advantages, which could enhance theperformance of electromechanical actuation systems.

SUMMARY OF THE APPLICATION

It is therefore an aim of the present disclosure to provide a novelcable-driven system using a magnetorheological fluid for torquetransmission.

Therefore, in accordance with a first embodiment of the presentapplication, there is provided a tensioning set comprising: an outputmember; a magnetorheological fluid clutch apparatus configured toreceive a degree of actuation (DOA) and connected to the output member,the magnetorheological fluid clutch apparatus being actuatable toselectively transmit the received DOA through the output member bycontrolled slippage; and a tensioning member being connected to theoutput member so as to be pulled by the output member upon actuation ofthe magnetorheological fluid clutch apparatus, a free end of thetensioning member adapted to exert a pulling action transmitted to anoutput when being pulled by the output member.

Further in accordance with the first embodiment, the output member andthe tensioning member are any one of a wheel or pulley and cable ortendon, and a chainring and chain.

Still further in accordance with the first embodiment, a hydraulictransmission is associated with the tensioning member.

Still further in accordance with the first embodiment, the hydraulictransmission comprises a master cylinder connected to the tensioningmember to convert the pulling action into hydraulic pressure, a slavecylinder adapted to transmit the hydraulic pressure to the output, andan hydraulic hose between the master cylinder and the slave cylinder fortransmission of hydraulic pressure therebetween.

Still further in accordance with the first embodiment, the hydraulictransmission is located between an end of the tensioning memberconnected to the output member, and the free end of the tensioningmember.

In accordance with a second embodiment of the present disclosure, thereis provided a system comprising: at least one of the tensioning set asdescribed above; and means configured to provide a force on the outputantagonistic to a transmission of the pulling action of the at least onetensioning set on the output.

Further in accordance with the second embodiment, the means forproviding the pulling action is another one of the tensioning set.

Still further in accordance with the second embodiment, all of thetensioning sets are configured to share a single power source providingthe DOA.

Still further in accordance with the second embodiment, the means forproviding the force is a biasing member.

Still further in accordance with the second embodiment, a brake systemis adapted to lock the output in a desired position while not in a freestate mode.

Still further in accordance with the second embodiment, the output isconstrained to movement along at least one degree of freedom (DOF); thepower source providing the DOA, the DOA being a rotational DOA; wherebymovement of the output in the at least one DOF is actuated bycontrolling an actuation of the magnetorheological fluid clutchapparatus of the at least one tensioning set.

Still further in accordance with the second embodiment, the output is amechanism formed of bodies interconnected by joints, the output beingconstrained by a number of the tensioning sets at least equal toDOF+1-Number of biasing members, DOF being the number of degrees offreedom of the mechanism.

Still further in accordance with the second embodiment, the output is ajoystick.

Still further in accordance with the second embodiment, the output is afriction clutch.

In accordance with a third embodiment of the present disclosure, thereis provided a robotic arm comprising: at least two bodies, with a baseone of the bodies configured to be connected to a base, and an end oneof the bodies configured to support a tool; at least one kinematic jointserially interconnecting the bodies, and providing at least one degreeof freedom (DOF) between the bodies; and at least two of the tensioningsets as described above, the tensioning sets exerting antagonisticpulling actions transmitted to the at least one kinematic joint; wherebymovement of the bodies relative to one another in the at least one DOFis actuated by controlling an actuation of the magnetorheological fluidclutch apparatuses of the tensioning sets.

Further in accordance with the third embodiment, each of the at leastone kinematic joint between each serially connected pair of the bodiesprovides at least two DOFs, the robotic arm being constrained by anumber of the tensioning sets at least equal to DOF+1-Number of biasingmembers, DOF being the number of degrees of freedom of an assembly ofthe bodies and the kinematic joints.

Still further in accordance with the third embodiment, the slavecylinders are connected to the bodies, and wherein the master cylindersand the magnetorheological fluid clutch apparatus are connected to abase.

Still further in accordance with the third embodiment, all of thetensioning sets are configured to share a single power source mounted tothe base.

Still further in accordance with the third embodiment, the at least onekinematic joint comprises two rotational joints sharing a commoncarriage, one of the two rotational joints rotationally connected to afirst of the bodies, and the other of the two rotational jointsrotationally connected to a second of the bodies.

In accordance with a fourth embodiment, there is provided a compressingset comprising: a magnetorheological fluid clutch apparatus configuredto receive a degree of actuation (DOA), the magnetorheological fluidclutch apparatus being actuatable to selectively transmit the DOA bycontrolled slippage; a master cylinder connected to magnetorheologicalfluid clutch apparatus to convert actuation thereof into hydraulicpressure, a slave cylinder adapted to transmit the hydraulic pressure toan output; and an hydraulic hose between the master cylinder and theslave cylinder for transmission of hydraulic pressure therebetween.

In accordance with a fifth embodiment of the present disclosure, thereis provided a system comprising: at least one of the compressing setdescribed above; and means configured to provide a force on the outputantagonistic to a transmission of the hydraulic pressure of the at leastone compressing set on the output.

Further in accordance with the fifth embodiment, the means for providingthe force is another one of the compressing set.

Still further in accordance with the fifth embodiment, all of thecompressing sets are configured to share a single power source providingthe DOA.

Still further in accordance with the fifth embodiment, the means forproviding the force is a biasing member.

Still further in accordance with the fifth embodiment, a brake system isadapted to lock the output in a desired position while not in a freestate mode.

Still further in accordance with the fifth embodiment, the output, theoutput being constrained to movement along at least one degree offreedom (DOF); the power source providing the DOA, the DOA being arotational DOA; whereby movement of the output in the at least one DOFis actuated by controlling an actuation of the magnetorheological fluidclutch apparatus of the at least one compressing set.

Still further in accordance with the fifth embodiment, the output is amechanism formed of bodies interconnected by joints, the output beingconstrained by a number of the compressing sets at least equal toDOF+1-Number of biasing members, DOF being the number of degrees offreedom of the mechanism.

In accordance with a sixth embodiment of the present disclosure, thereis provided a method for controlling movements of an output in at leastone degree of freedom (DOF), comprising: obtaining at least one degreeof actuation (DOA); controlling a slippage of a first magnetorheologicalfluid clutch apparatus to convert at least part of the DOA into anaction on the output in a first direction of the at least one DOF with afirst member; and controlling a slippage of at least a secondmagnetorheological fluid clutch apparatus to convert at least part ofthe DOA into an action on the output in a second direction of the atleast one DOF with a second member, antagonistically to the action bythe first magnetorheological fluid clutch apparatus.

Still further in accordance with the sixth embodiment, obtaining the atleast one DOA comprises obtaining the at least one DOA from a commonpower source for all of the magnetorheological fluid clutch apparatuses.

Still further in accordance with the sixth embodiment, controlling theslippage of the first magnetorheological fluid clutch apparatuscomprises converting at least part of the DOA into a pulling action onthe output with the first member being a tensioning member.

Still further in accordance with the sixth embodiment, controlling theslippage of the second magnetorheological fluid clutch apparatuscomprises converting at least part of the DOA into a pulling action onthe output with the second member being another tensioning member.

Still further in accordance with the sixth embodiment, controlling theslippage of the first magnetorheological fluid clutch apparatuscomprises converting at least part of the DOA into a pushing action onthe output with the first member being a compressing member.

Still further in accordance with the sixth embodiment, controlling theslippage of the second magnetorheological fluid clutch apparatuscomprises converting at least part of the DOA into a pushing action onthe output with the second member being another compressing member.

Still further in accordance with the sixth embodiment, the output hasmore than one DOF and wherein controlling the slippage of themagnetorheological fluid clutch apparatuses comprises antagonisticallyopposing the actions of the magnetorheological fluid clutch apparatusesfor each of the DOFs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a magnetorheological fluid clutchapparatus used in cable-driven systems of the present disclosure;

FIG. 2 is a schematic view of a power distribution arrangement in acable-driven system in accordance with the present disclosure, usingmagnetorheological fluid clutch apparatuses;

FIG. 3 is a schematic view of a cable-driven system using a common powersource with a pair of magnetorheological fluid clutch apparatuses forantagonistic displacement of an end effector;

FIG. 4 is a schematic view of a cable-driven system using a common powersource with magnetorheological fluid clutch apparatuses for displacementof an end effector in two rotational degrees of freedom;

FIG. 5 is a perspective view of the cable-driven system of FIG. 4, setup with two pairs of magnetorheological fluid clutch apparatuses forantagonistic displacement of an end effector;

FIG. 6A is a schematic view of a cable-driven system using a commonpower source with a pair of magnetorheological fluid clutch apparatusesto control movements of bodies serially connected by kinematic joints,with power sources on the bodies;

FIG. 6B is a schematic view of a cable-driven system using a commonpower source with a pair of magnetorheological fluid clutch apparatusesto control movements of bodies serially connected by kinematic joints,with a shared power source on a base;

FIG. 7A is a perspective view of a robotic arm based on the system ofFIGS. 2 to 6B;

FIG. 7B is a perspective view of an intermediate body of the robotic armof FIG. 7A;

FIG. 7C is a perspective view of a power module of the robotic arm ofFIG. 7A;

FIG. 7D is a perspective view of another embodiment of the power moduleof the robotic arm of FIG. 7A;

FIG. 7E is a cross-section view of the power module of FIG. 7D;

FIG. 8 is a schematic view of a magnetorheological servo hydraulicactuator system used in conjunction with a vehicle friction clutch; and

FIG. 9 is a schematic view of a fluid-driven system using a common powersource with a pair of magnetorheological fluid clutch apparatuses forantagonistic displacement of an end effector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and more particularly to FIG. 1, there isillustrated a generic magnetorheological (MR) fluid clutch apparatus 10configured to provide a mechanical output force based on a receivedinput current. The MR fluid clutch apparatus 10 of FIG. 1 is asimplified representation of a MR fluid clutch apparatus that may beused in the systems described hereinafter. The MR fluid clutch apparatusthat is used in the systems described hereinafter may have additionalcomponents and features, such as drums, redundant electromagnets, MRfluid expansion systems, etc.

The MR fluid clutch apparatus 10 has a driving member 12 with radialdisks 13, this assembly also known as input rotor. The MR fluid clutchapparatus 10 also has a driven member 14 with annular plates 15intertwined with the radial disks 13 to define an annular chamber(s)filled with an MR fluid 16, the annular chamber being delimited by acasing 17 that is integral to the driven member 14. The assembly of thedriven member 14 and annular plates 15 is also known as the outputrotor. In the example of FIG. 1, the driving member 12 may be an inputshaft in mechanical communication with a power input, and driven member14 may be in mechanical communication with a power output (i.e., forceoutput, torque output). MR fluid 16 is a type of smart fluid that iscomposed of magnetisable particles disposed in a carrier fluid, usuallya type of oil. When subjected to a magnetic field, the fluid mayincrease its apparent viscosity, potentially to the point of becoming aviscoplastic solid. The apparent viscosity is defined by the ratiobetween the operating shear stress and the operating shear rate of theMR fluid comprised between opposite shear surfaces—i.e., that of theradial disks 13 on the drive side, and that of the annular plates 15 andof the walls of the casing 17 in the annular chamber 17. The magneticfield intensity mainly affects the yield shear stress of the MR fluid.The yield shear stress of the fluid when in its active (“on”) state maybe controlled by varying the magnetic field intensity produced byelectromagnet 18 integrated in the casing 17, i.e., the input current,via the use of a controller. Accordingly, the MR fluid's ability totransmit force can be controlled with the electromagnet 18, therebyacting as a clutch between the members 12 and 14. The electromagnet 18is configured to vary the strength of the magnetic field such that thefriction between the members 12 and 14 is low enough to allow thedriving member 12 to freely rotate with the driven member 14 and viceversa.

Referring to FIG. 2, a cable-driven system in accordance with thepresent disclosure is generally shown at 20. The cable-driven system 20has n MR fluid clutch apparatuses 10 receiving a torque input from asingle power source 21 via a common power shaft 22 driven by the powersource 21. For example, the power source 21 may be an electric motor,although other types of power sources may be used, such as hydraulicmotors to name one among numerous other examples.

The MR fluid clutch apparatuses 10 are each equipped with an outputmember 23 upon which is mounted a cable 24, to form a tensioning set.The output member may practically be connected to the driven member 14(FIG. 1) of the MR fluid clutch apparatuses 10 so as to rotatetherewith. However, the output member may also have mechanisms betweenthe driven member 14 and the output member 23 instead of being a directdrive. For example, the output member 23 may incorporate a reductiongearbox. The expression “output wheel” is used as an encompassingexpression for equivalent parts, such as a pulley, a chainring, asprocket, a nut, a screw, lever arm, etc. Likewise, the expression“cable” is used as an encompassing expression for equivalent parts, suchas a tendon, rope, belt, chain, and like tensioning members. Theselection of the type of cable is based on the type of output wheel. Thecable 24 has an end attached to the output wheel 23, a free end 25attached to an output component, with a length of the cable being woundabout the output wheel 23. A rotation of the output wheel 23, forinstance as driven by the driven member 14 (FIG. 1), may wind additionalcable length onto the output wheel 23, resulting in a pulling action atthe free end of the cable 24. A pulling action on the free end 25 mayalternatively result in an unwinding of the cable 24 from the outputwheel 23, for instance when the MR fluid clutch apparatus 10 is in aslippage condition, i.e., when the pulling action on the free end 25exceeds the force produced by the driven member 14. The cable-drivensystem 20 has n outputs for a single degree of actuation. Usingcontinuous-slippage MR fluid clutch apparatuses 10 as tensioners in thecable-driven system 20 allows torque distribution from a single powersource 21 amongst many outputs in order to drive possibly multiple DOFs.Although the MR fluid clutch apparatuses 10 can only produce torque inthe direction they are being driven by the power source, this is not anissue in the case of cable-driven systems because of the cables'intrinsic inability to effectively transmit compressive loads.

One particular embodiment of the cable-driven system of FIG. 2 is shownas 30 in FIG. 3. As the cable-driven system 30 has components in commonwith the cable-driven system 20 of FIG. 2, like components will bearlike reference numerals. The cable-driven system 30 has a pair of the MRfluid clutch apparatuses, one of which is shown at 10A and the other ofwhich is shown as 10B, the apparatuses 10A and 10B being connected to acommon power source (not shown) as it is the case for the system 20 ofFIG. 2. The MR fluid clutch apparatuses 10A and 10B are connected viacables 24 to a common end effector 31. The common end effector 31 isillustrated as being a pivoting arm, mounted to a base 32 by pivot 33.Accordingly, the end effector 31 is movable in one rotational degree offreedom (DOF). In spite of being driven by the common power source, theMR fluid clutch apparatuses 10A and 10B provide antagonistic pullingactions on the end effector 31, to enable reciprocating movement. Also,although the end effector 31 is shown as being movable in one rotationalDOF, the end effector 31 could be connected to the base 32 by atranslation joint, whereby the system 30 would provide a translationalDOF. It is also considered to provide a single MR fluid clutch apparatus10 and thus a single cable 24 connected to the end effector 31, with anantagonistic force provided by a biasing member such as a linkage,spring, gravity, other type of actuators, etc (not shown). The biasingmember may also include more complex mechanisms, such as a servo system,linear actuators, etc. In other words, any mechanism capable of opposingan antagonistic force to the end effector 31 may be used. This isapplicable for given embodiments provided below as well.

In typical antagonistic cable-driven actuation systems, one actuator perdegree-of-freedom (DOF) is generally used. Each actuator must thereforebe designed to satisfy the maximum load for the degree-of-freedom it isdriving. The DOF is actuated by two actuators because of the cables'inability to transmit compressive loads. Each DOF is hence actuated bytwo antagonistic actuators and generally only one is being activated ata time because of their opposing effect. For example, if a load isrequired to be produced in the clockwise direction, a clockwise actuator(CWA) is powered and the counter-clockwise actuator (CCWA) is unpoweredand vice-versa if the load is required to be produced in the otherdirection.

In contrast, when centralizing the power source 21 (FIG. 2) in thesystem 30 of FIG. 3, the resulting system may lead to a compact andlightweight design. Moreover, since the continuous-slippage MR fluidclutch apparatuses uncouple the inertia of the power source 21 from theend effector 31, a lightweight power source, such as a high-speedelectric motor coupled with a high-ratio reduction gearbox can be usedwithout impacting the system's dynamic performance. Furthermore, therequired load for the power source 21 can be tailored according to theapplication, leading to further weight reduction. For example, as thecable-driven system 30 utilizes a purely antagonistic actuationarrangement, the power source 21 is not required to produce the sum ofthe load capacity of both continuous-slippage MR fluid clutchapparatuses 10 it is driving, since only one of each pair can be activeat the same time. The power source 21 can therefore be designed for onlyapproximately one half of the total load requirement (i.e., the“offstate or free state” power of the clutch apparatus in slippage beinggreater than zero). This principle applies not only in the case ofantagonistic architectures but it also applies in any application wheremultiple outputs do not need to be actuated simultaneously at theirmaximum load.

When maintained in slippage and used with a geared motor as power source21, the MR fluid clutch apparatuses 10 in the cable-driven system 30decouple the dynamic behavior of the motor from the outputs resulting ina low output inertia and high control quality since the high outputinertia of the geared motor 21 is not reflected at the system output.The cable-driven system 30 may also provide an increased force accuracyas the non-linear behaviors of the geared motor (e.g. cogging, gearbacklash, friction) are filtered by the MR fluid clutch apparatuses. Thecable-driven system 30 also has relatively low mass and a reduced numberof components since loads generated by a common geared motor 21 can beshared between a plurality of outputs. In some applications, thecable-driven system 30 may be reliable as a faulty geared motor can bedisconnected from the output following clutch disengagement, when aredundant motor is available as back-up.

Referring to FIGS. 4 and 5, yet another embodiment using the concepts ofthe cable-systems 20 and 30 is illustrated at 40. As the cable-drivensystem 40 has components in common with the cable-driven system 20 ofFIG. 2, like components will bear like reference numerals. Thecable-driven system 40 has four MR fluid clutch apparatuses 10. The MRfluid clutch apparatuses 10 are connected to a common power source 21.

The MR fluid clutch apparatuses 10 are connected via cables 24 to acommon end effector 41. The common end effector 31 is illustrated asbeing a rotating arm, mounted to a base 42 by a gimbal joint 43 (orother joint such as a universal joint and spherical joint). Accordingly,the end effector 41 is movable in two rotational DOFs, although otherjoint arrangements could be provided to constrain the end effector tomovements along one translation DOFs and one rotational DOF, or twotranslation DOFs. In spite of being driven by the common power source21, the MR fluid clutch apparatuses 10 provide antagonistic andcomplementary pulling actions on the end effector 41, to enable movementin the at least two rotational DOFs.

In the specific configuration of FIG. 5, each of the two rotational DOFsis controlled by a respective tensioning set of two antagonistic MRfluid clutch apparatuses 10 (i.e., disposed on opposite sides of thegimbal joint 43). However, it is possible to control the two rotationalDOFs with only three of the MR fluid clutch apparatuses 10. Likewise,the four MR fluid clutch apparatuses 10 of FIG. 5 could be used tocontrol three rotational DOFs, by crossing the cables 25 to control therotational about the longitudinal axis of the end effector 41.

The cable-driven system 40 may utilize a high-speed electric motor witha high reduction ratio gearbox as the single centralized power source21. Bevel gears 44 (enclosed in casing 50 in FIG. 5) are used totransmit the power to the driving members of the four MR fluid clutchapparatuses 10 that apply tension to the cables 24. Bevel gears 44 ofantagonistic tensioning sets are coaxial and diametrically opposedrelative to a drive bevel gear. Cable guides 51 may be present to routethe cables 24 within a confined volume.

The cable-driven systems 30 and 40 may be adapted and optimized to matchparticular requirements of specific applications. For instance, anarrangement of the cable-driven system 40 could be used in an activejoystick. Active joysticks are able to modulate the force-feedback tothe operator in real time, as opposed to traditional passive joysticksfor which the force-to-displacement characteristics cannot be changed.Active joysticks based on the cable-driven system 40 may have highdynamic response, high force capacity and be lightweight. End uses ofsuch active joysticks based on the cable-driven systems 30 and 40 arenumerous in many fields of application, including non-exclusivelyconsumer mobility vehicles, heavy equipment, material handlingequipment, medical applications (robotically-assisted surgery),aerospace, etc). In another instance, an arrangement of the cable-drivensystem 40 could be used as a robotic arm. In another instance, thecable-driven system 40 could be used to direct a fluid(s) of a hydrauliccircuit. In another instance, of the cable-driven system 40 could beused to direct a gas in order to act as a thrust vectoring system todirect an aircraft.

Referring to FIGS. 6A and 6B, yet another embodiment using the conceptsof the cable-systems 20, 30 and 40 is illustrated at 60. As thecable-driven system 60 has components in common with the cable-drivensystem 20 of FIG. 2, like components will bear like reference numerals.The cable-driven system 60 can be described as having bodies 60A, 60B,60 n (also commonly known as link members or linkages in robotics),being connected to each other by kinematic joints 61 (pivots, balljoints, sliders, etc.) and by limited-stiffness elements such as cables24. The cable-driven system 60 has a power module or source 62 in a base63. The power source 62 transmits its output to a pair of MR fluidclutch apparatus 10 each supporting an output wheel 23 and cable 24,with the MR fluid clutch apparatuses 10 being assembled to the base 63so as to share the power output from the power source 62 (e.g., insimilar fashion to the arrangements shown in FIGS. 2-5).

The free ends of the cables 24 are connected to the body 60A, so as toexert a pulling action on the body 60A. The body 60A is constrained togiven movements by its connection to the kinematic joints 61, and thepulling action of the cables 24 is controlled by the actuation of the MRfluid clutch apparatuses 10 so as to selectively control movements ofthe body 60A. Bodies 60A, 60B, 60 n may have a similar configuration asthe base 63, i.e., each with its own power source 62, MR fluid clutches10, output wheels 23 and cables 24, serially connecting the bodies 60A,60B, 60 n. Bodies 60A, 60B, 60 n may also have a different configurationthan that including the base 63. For example, each or a few of thebodies 60A, 60B, 60 n may have MR fluid clutch apparatuses 10, outputwheels 23 and cables 24, serially connecting the bodies 60A, 60B, 60 n,all of the bodies with a MR fluid clutch apparatus 10 using the powercoming from the base source 62 (i.e., power could be distributed by arotating flexible shaft).

Alternatively, as shown in FIG. 6B, a single power source 62 in the base63 may be shared by a plurality of MR fluid clutch apparatuses 10 on thebase 63, with cable guides 65 on the proximal body 60A can apply tensionon the distal body 60B, etc. The cable guides 65 may be idler pulleys,posts, etc.

Again, tension in the limited-stiffness elements (i.e., the cables 24)is controlled by the MR fluid clutch apparatuses 10. Hence, loadsapplied on the bodies 60A, 60B, 60 n, and their motion relative to eachother can be accurately controlled with high dynamic performance.

Referring to FIG. 7A-7C, an embodiment of the cable systems of FIGS. 6Aand 6B is shown, in a robotic arm 70. The robotic arm 70 is of the typehaving a gripper 71 at its output end. The gripper 71 is one amongnumerous possible tools that may be used as the end of the robotic arm70, and is simply provided as an example. The gripper 71 is for exampleactuated independently from the actuation of the robotic arm 70, as thegripper 71 need only displace its fingers, and be rotated at its wrist.For illustrative purposes, other tools that could be used asalternatives to the gripper 71 include pliers, a drill, pincers, to namebut a few.

The robotic arm 70 is shown as being a 4-DOF arm with bodies 60A, 60Band 60C, in that 4 rotational DOFs are provided between the base 63 andthe part of the body 60C supporting the gripper 71. Again, this is oneof numerous possibilities, as it has been explained for FIGS. 6A and 6Bthat there may be more or fewer bodies, with more or fewer DOFs, theDOFs being translations and/or rotations.

For ease of explanation and to avoid redundancies, only the intermediatebody 60B, shown in FIG. 7A as being between body 60A and 60C, isdescribed in detail with reference to FIG. 7B, but the base body 60A andthe end body 60C have similar components. The intermediate body 60B inshown being connected to the end body 60C by way of the kinematic joints61, the kinematic joints 61 incorporating several components. Thekinematic joint 61 may indeed include a first rotational joint 72 fixedto the body 60B, the first rotational joint 72 having a pair of pulleysor equivalent, 72A and 72B, both concurrently rotatable about axis θ1.The pulleys 72A and 72B are concurrently rotatable as they are fixed toone another. A rotation of the pulleys 72A and 72B will result in arotation of carriage 73, again about axis θ1. A mirror or similararrangement is also provided at the end of the end body 60C interfacedto the intermediate body 60B, as shown by the rotational joint 74, thecarriage 73 being shared by rotational joints 72 and 74 as part of thekinematic joint 61. Therefore, the kinematic joint 61 provides two ofthe four rotational DOFs of the robotic arm 70, about axes 81 and 02,respectively by way of joint 72 and joint 74.

The pulleys 72A and 72B are respectively connected to cables orequivalents 24A and 24B, but in opposite winding orientations, such thatcable 24A provides a clockwise rotation, and cable 24B provides theantagonistic counterclockwise rotation. It is contemplated to route thecables 24A and 24B directly to the MR fluid clutch apparatuses, usingcable guides such as the one shown at 65 in FIG. 6B. However, the use ofan hydraulic transmission is shown as an alternative. In given systemsinvolving more DOFs and a wider range of movement, an hydraulictransmission may be a practical alternative as routing of hydraulichoses may be less complex than cable routing.

For the rotational joint 72, the antagonistic actuation is provided byslave cylinders 75A and 75B. Slave cylinder 75A has a rod 76Adisplaceable along XA, to pull the cable 24A and thus rotate the pulley72A, i.e., the components affixed with “A”. Likewise, slave cylinder 75Bhas a rod 76B displaceable along XB, to pull the cable 24B and thusrotate the pulley 72B, i.e., the components affixed with “B”. In thedescription, cables are used here in order to provide greater amplitudeof movement. However, similarly to a mechanism described subsequentlyfor FIG. 9, the piston rods 76A, 76B, 76C could be attached directly tothe pulleys 72A, 72B, 72C, provided an appropriate joint (e.g., swiveljoint) is fitted between the pistons rods 76 and the correspondingpulley 72, and provided that the cylinders 75 may rotate relative to thestructural components of the body 60. Each of the slave cylinders 75Aand 75B has its own dedicated MR fluid clutch apparatus 10, as shownlater in FIG. 7C, providing the necessary hydraulic pressure and fluidmovement to cause antagonistic force control, which may lead tocontrolled movements of the rotational joint 72.

FIG. 7B also shows another pair of slave cylinders 75C and 75D, orientedtoward the base body 60A. The slave cylinders 75C and 75D controlanother rotational DOF, in the same manner as described for therotational joint 72. The components at the right-hand side of thefigures are essentially the same as on the left-hand side, whereby theoperation of the right-hand side is self-explanatory. The body 60B isshown as using a frame member 60B1 to act as a rigid link between thekinematic joints 61. The body of the cylinders 75 could also be used asframe members, along with connecting plates and associated hardware. Anypossible frame arrangement is considered and usable to ensure that therotatable components, i.e., the rotational joints 72 and 74 inter alia,may rotate while their axes are fixed in position.

Referring to FIG. 7C, the generic power module 62 is illustrated ashaving the electric motor 21 driving the output shaft 22. The powermodule 62 is used to actuate and control the movements of the roboticarm 70. Advantageously, the weight of the power module 62 is notsupported by the robotic arm 70, and may instead be on a separatestructure, such that the robotic arm 70 need not bear the weight of thepower module 62. MR fluid clutch apparatuses 10A-10H, concurrentlyreferred to as 10, are each secured to the output shaft 22. Each MRfluid clutch apparatus 10 has a pulley or equivalent 23, about which iswound a cable or equivalent 24, in similar fashion to the previouslydescribed embodiments. By way of the cables 24, each MR fluid clutchapparatus 10 pulls on a respective rod 77 (from rods 77A-77H). The rods77 are each associated with a master cylinder 78 (i.e., one of thecylinders 78A-78H), whereby the pull will generate an hydraulic flow orpressure supply at the hydraulic hose 79 (i.e., pipe, tube, tubing,etc). Looking at FIG. 7A, the harness of hoses 79 (i.e., 79A-79H)diverges into the individual hoses 79 each reaching an associated slavecylinder, as shown in FIG. 7A, but not in FIG. 7B in which the hoses 79are absent to simplify the figure. For example, the master cylinders 78Aand 78B in FIG. 7C may respectively be connected to the slave cylinders75A and 75B in FIG. 7B. Hence, the master cylinders 78 convert amechanical pull produced by the MR fluid clutch apparatuses 10 into ahydraulic pressure, the hydraulic pressure being reconverted into amechanical pull by the slave cylinders 75, to cause the antagonisticforces and movements. The robotic arm 70 therefore benefits from thedynamic response of MR fluid clutch apparatuses 10 in its movements. Themultiple DOFs of the robotic arm 70 may be actuated using a single powersource, namely the motor 21, with the control of the movements providedby the selective coupling input from the MR fluid clutch apparatuses 10,operated by a controller (including a processor unit and appropriatecontrol modules).

Each pair of antagonistic slave cylinders (e.g., the pair 75A and 75B)provide antagonistic forces, when one of the associated MR fluid clutchapparatuses, 10A, causes a pulling action by pulling on the cable 24A(and thus winding the cable 24A on the pulley 23A), the other MR fluidclutch apparatus 10B may be in controlled slippage. Controlled slippagecauses a release in pressure in the hydraulic transmission and cable24B. The cable 24B is consequently wound about the pulley 72B (FIG. 7B).Consequently, the rod 76B is pulled by the cable 24B, whereby the slavecylinder 75B becomes temporarily master to the master cylinder 78B (FIG.7C). This results in a retraction of the rod 77B into the mastercylinder 78B, and an unwinding of the cable 24B at the MR fluid clutchapparatus 10B. Therefore, as suggested previously, the electric motor 21will not be transmitting full forces to all tensioning setssimultaneously, due to the antagonistic operation of pairs of thetensioning sets.

Referring to FIGS. 7D and 7E, another arrangement of the power module isillustrated as 62′, and has the electric motor 21 driving the input ofmultiple MR clutches apparatuses 10. The power module 62′ is used toactuate and control the movements of the robotic arm 70 (FIGS. 7A-7B).The MR fluid clutch apparatuses 10A-10H, concurrently referred to as 10,are each operatively connected to one another for transmission of thepower input of the motor 21 to all of the MR fluid clutch apparatuses10. The MR fluid clutch apparatuses 10 are arranged in two rows, a firstrow including MR fluid clutch apparatuses 10A-10D rotating in a firstdirection as meshed to one another, and a second row including MR fluidclutch apparatuses 10E-10H rotating in a second direction as meshed toone another, opposite the first direction. The opposite directions maybe achieved by a gear arrangement featuring gear 21A for the first row,and gear 21B for the second row, receiving the single rotation outputfrom the motor 21 to rotate in opposite directions.

As shown in FIG. 7E, each antagonistic pair of MR fluid clutchapparatuses, shown by the antagonistic pair 10A and 10E, acts on anidler nut 14′ that is part of the driven member 14. The driven member 14is shared by the antagonistic pair 10A and 10E. However, the drivemember 12A will rotate the driven member 14 in a first direction,whereas the drive member 12E will rotate the driven member 14 in theopposite direction. Hence, each MR fluid clutch apparatus of anantagonistic pair (e.g., 10A/10E) act antagonistically on the idler nut14′. The idler nut 14′ may be connected to a threaded shaft 14″ or likeany other rotation to translation type of mechanism, such as ball screw,that will convert the rotation from the MR fluid clutch apparatuses 10to a reciprocating translation in direction X, reciprocating as per theopposite directions of rotation. The threaded shaft 14″ is connected atits opposed ends to the piston rods 77A and 77E acting on single actionmaster cylinders 78A and 78E or on a double acting master cylinder (notillustrated). Piston rods 77A and 77E may only translate, its rotationabout its main axis being blocked by a mechanism (not illustrated).Other power module arrangements are considered as well, the embodimentof FIGS. 7C and 7E being two illustrations of possible embodiments.

The cable-driven system described above use MR fluid clutch apparatusesin conjunction with cables and output wheels, including all othervariations or embodiments of the cables and output wheels as describedabove.

The number of clutch apparatuses 10 required to fully constrain andcontrol an assembly on bodies should be superior or equal toDOF+1-Number of biasing members, DOF being the number of degrees offreedom of the mechanism.

It is to be noted that a number of clutch apparatuses 10 superior toDOF+1-Number of biasing members creates a redundancy, if the clutchesand the attaching points on the bodies are correctly positioned.

Referring to FIG. 8, a magnetorheological servo hydraulic actuatorsystem is generally shown at 80, and used in conjunction with a vehiclefriction clutch, schematically shown as 90. The system 80 has componentsin common with the cable-driven system 20 of FIG. 2, whereby likecomponents will bear like reference numerals, for instance for the MRfluid clutch apparatus 10, the power source 21 (e.g., an electricmotor), the output wheel 23 and the cable 24. The system 80 mayadditionally comprise a gearbox 81. The magnetorheological servohydraulic actuator system 80 is designed to control the torque that isbeing transmitted from a vehicle engine to its driving wheels throughthe friction clutch 90. The system 80 may be used with vehicles havingmanual transmissions or automated manual transmissions, for instance toeliminate the use of the clutch pedal and/or minimize gear shiftingtime.

In the system 80, the free end of the cable 24 is attached to the rod ofa master cylinder 82. The master cylinder 82 is used to move remotelyslave cylinder 83 through hydraulic hoses and reservoir 84. The slavecylinder 83 moves fork 85 to engage/disengage the vehicle's frictionclutch 90.

In operation, the rotational speed of the power source 21 is typicallylimited to a value that ensures the required translational speed of athrow-out bearing 91 results in satisfactory system performance.

When the MR fluid clutch apparatus 10 transmits torque, the cable 24winds around the output wheel 23, thereby pulling on the rod of themaster cylinder 82. The hydraulic fluid is displaced through hoses fromthe master cylinder 82 to the slave cylinder 83 whose output moves thethrow-out bearing 91 of the vehicle friction clutch 90, by way of thefork 85. When the current is decreased in the MR fluid clutch apparatus10, spring 92 of the friction clutch 90 helps for its reengagement byproviding an antagonistic action. The current level in the MR fluidclutch apparatus 10 is controlled and adjusted to avoid damage on thefriction interfaces of the vehicle clutch 90. When the current isremoved, the low friction torque of the unpowered MR clutch apparatuscauses a minimal tension in the cable 24.

If this residual tension in the cable 24 is found to be too high, thesystem 80 may further include a constant low-force device, such as aconstant torsion spring mounted on the output wheel 23, installed inparallel and referenced to the chassis to counteract any parasitictension while not significantly impacting the on-state characteristicsof the system. Such device would mitigate any impact the torque couldhave on the vehicle friction clutch 90 when the MR fluid clutchapparatus 10 is not powered, such as avoiding loading the throw-outbearing 91 which could otherwise reduce its life.

In the system 80, the hydraulic circuit (i.e., master cylinder 82, slavecylinder 83 and reservoir 84) are used purely as a load transmissiondevice and the electric hardware could be located in the interior orunder the hood of the car. However, a different packaging could allowremoval of the hydraulic system by directly attaching the driven end ofthe cable 24 to the fork 85 of the vehicle friction clutch 90.

The system 80 may be used in two operation modes, “launch” and “gearshift”. In “launch” mode, the role of the system 80 is to ensure anadequate traction of the tires on the road during the launch of thevehicle by controlling the torque transmitted by the friction clutch 90.In “gear shift” mode, role of the system 80 is to quickly disengage theclutch 90 when the driver initiates a gear change and smoothly reengagethe clutch 90 when the gear change is completed.

The systems 20, 30, 40, 50, 60 and 80 are typically equipped with acontroller (i.e., a processing unit) and output sensors to control thecurrent sent to the MR fluid clutch apparatuses 10 to achieve therequired output response. The controller therefore controls movements ofan output in one or more DOFs when the systems 20, 30, 40, 50, 60 and 80obtain the DOA. The controller controls a slippage of a firstmagnetorheological fluid clutch apparatus to convert at least part ofthe DOA into a pulling of the output in a first direction of the atleast one DOF with a first tensioning member; and controls a slippage ofat least a second magnetorheological fluid clutch apparatus to convertat least part of the DOA into a pulling of the output in a seconddirection of the at least one DOF with a second tensioning member,antagonistically to the pulling by the first magnetorheological fluidclutch apparatus. The second magnetorheological fluid clutch apparatusmay be replaced by a biasing member—gravity acting on the object or theflexibility of the member are also included in the list of biasingmember —, the biasing member not controllable but nonetheless offeringan antagonistic action to the first magnetorheological fluid clutchapparatus 10. The DOA may be obtained from a common power source for allof the magnetorheological fluid clutch apparatuses. In some of thesystems, the output has two DOFs, such that controlling the slippage ofthe first and the second magnetorheological fluid clutch apparatuses isto antagonistically pull the output in a first of the DOFs, while theslippage of third and the fourth of the magnetorheological fluid clutchapparatuses is controlled to antagonistically pull the output in asecond of the DOFs.

Referring to FIG. 9, a system operated with a similar antagonisticapproach is shown at 100. However, instead of cables, the system 100uses fluid pressure to actuate movements of an output, by way ofhydraulic transmission units, similar to those employed in the roboticarm 70 of FIGS. 7A-7C. In the illustrated embodiment, the system 100 hasa pair of MR fluid clutch apparatuses 10 which, although not shown, mayreceive power from a common power source, for instance as in FIG. 2 orin FIG. 4. However, for simplicity, the power source and associatedtransmission is not illustrated in the FIG. 9. The driven member 14 ofeach MR fluid clutch apparatus 10 is an arm pivotally connected to apiston 101 of a master cylinder 102, by way of a rod 103. The system 100may further have a flexible hose 104 extending from the master cylinder102 to another cylinder, the slave cylinder 105. This slave cylinder 105has a piston 106 and its rod 107 pivotally connected to an output 108pivotally mounted to a ground at pivot 109.

In operation, the actuation of one of the MR fluid clutch apparatuses 10results in movement of its associated piston 101 in the respectivemaster cylinder 102. Pressurized fluid may as a result travel from themaster cylinder 102, through the hose 104, and into the slave cylinder105. This will cause a movement of the piston 106 that will push theoutput 108. The actuation of the other of the MR fluid clutchapparatuses 10 may result in a reciprocating movement of the output 108,in this illustrated embodiment of one rotational DOF.

Accordingly, the system 100 operates in a similar antagonistic approachas the systems 20, 30, 40, 50, 60, 70 and 80, yet with a pushing action(compressive load) instead of a pulling action (tensioning load) as whencables are used, whereby the system 100 has compressive sets as opposedto tensioning sets. The system 100 may be arranged to provide additionaldegrees of freedom of output, for example with an arrangement similar tothat of FIGS. 4, 5, 6 and 7. As an alternative to the presence of two MRfluid clutch apparatuses 10 in FIG. 9, the system 100 may use otherforces to perform the antagonistic opposition, such as a spring,gravity, etc, against the action of one of the MR fluid clutchapparatuses 10.

It is to be noted that both hoses could be plugged in different chambersof a same piston body, at the input or the output, the antagonisticopposition being applied on the piston, the rod transmitting the forceto the end effector.

In yet another embodiment, it is considered to provide a pair of onetensioning set (e.g., as in systems 20, 30, 40, 50, 60, 70 and 80) withone compressive set (e.g., as in system 100), to provide antagonisticforces on a same DOF of an output. Among possibilities offered by suchan arrangement, the anchor point for the tensioning set and thecompressive set can be on the same side, same area and/or same locationon the output. This may be a valuable features when space in scarce onone side of the output.

Any one of these systems 20, 30, 40, 50, 60, 80 and 100 may use a brakethat can immobilise the output in the driven position for an extendedperiod of time without having to activate the MR fluid clutch apparatus10 that leads to the driven position. The purpose of this is to limitthe wear of the MR fluid in the MR fluid clutch apparatus 10 while thesystem is under the influence of a spring force or external force whilethe system is kept in an immobile state.

The invention claimed is:
 1. A compressing set comprising: amagnetorheological fluid clutch apparatus configured to receive a degreeof actuation (DOA), the magnetorheological fluid clutch apparatus beingactuatable to selectively transmit the DOA by controlled slippage; amaster cylinder connected to magnetorheological fluid clutch apparatusto convert actuation thereof into hydraulic pressure, a slave cylinderadapted to transmit the hydraulic pressure to an output; and anhydraulic hose between the master cylinder and the slave cylinder fortransmission of hydraulic pressure therebetween.
 2. A system comprising:at least one of the compressing set according to claim 1; and meansconfigured to provide a force on the output antagonistic to atransmission of the hydraulic pressure of the at least one compressingset on the output.
 3. The system according to claim 2, wherein the meansfor providing the force is another one of the compressing set.
 4. Thesystem according to claim 3, wherein all of the compressing sets areconfigured to share a single power source providing the DOA.
 5. Thesystem according to claim 2, wherein the means for providing the forceis a biasing member.
 6. The system according to claim 2, furthercomprising a brake system adapted to lock the output in a desiredposition while not in a free state mode.
 7. The system according toclaim 2, further comprising: the output, the output being constrained tomovement along at least one degree of freedom (DOF); the power sourceproviding the DOA, the DOA being a rotational DOA; whereby movement ofthe output in the at least one DOF is actuated by controlling anactuation of the magnetorheological fluid clutch apparatus of the atleast one compressing set.
 8. The system according to claim 2, whereinthe output is a mechanism formed of bodies interconnected by joints, theoutput being constrained by a number of the compressing sets at leastequal to DOF+1-Number of biasing members, DOF being the number ofdegrees of freedom of the mechanism.
 9. The system according to claim 2,wherein the means for providing the force is a tensioning set includinganother magnetorheological fluid clutch apparatus configured to receivea degree of actuation (DOA) and connected to the output, the othermagnetorheological fluid clutch apparatus being actuatable toselectively transmit the received DOA through the output member bycontrolled slippage; and a tensioning member being connected to theoutput so as to be pulled by the output upon actuation of the othermagnetorheological fluid clutch apparatus, a free end of the tensioningmember adapted to exert a pulling action transmitted to an output whenbeing pulled by the output member.
 10. The system according to claim 9,wherein the output member and the tensioning member are any one of awheel or pulley and cable or tendon, and a chainring and chain.